import { describe, expect, test } from "bun:test";
import { groupMessagesByApiRound } from "../grouping";

function makeMsg(type: "user" | "assistant" | "system", id: string): any {
  return {
    type,
    message: { id, content: `${type}-${id}` },
  };
}

describe("groupMessagesByApiRound", () => {
  // Boundary fires when: assistant msg with NEW id AND current group has items
  test("splits before first assistant if user messages precede it", () => {
    const messages = [makeMsg("user", "u1"), makeMsg("assistant", "a1")];
    const groups = groupMessagesByApiRound(messages);
    // user msgs form group 1, assistant starts group 2
    expect(groups).toHaveLength(2);
    expect(groups[0]).toHaveLength(1);
    expect(groups[1]).toHaveLength(1);
  });

  test("single assistant message forms one group", () => {
    const messages = [makeMsg("assistant", "a1")];
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(1);
  });

  test("splits at new assistant message ID", () => {
    const messages = [
      makeMsg("user", "u1"),
      makeMsg("assistant", "a1"),
      makeMsg("assistant", "a2"),
    ];
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(3);
  });

  test("keeps same-ID assistant messages in same group (streaming chunks)", () => {
    const messages = [
      makeMsg("assistant", "a1"),
      makeMsg("assistant", "a1"),
      makeMsg("assistant", "a1"),
    ];
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(1);
    expect(groups[0]).toHaveLength(3);
  });

  test("returns empty array for empty input", () => {
    expect(groupMessagesByApiRound([])).toEqual([]);
  });

  test("handles all user messages (no assistant)", () => {
    const messages = [makeMsg("user", "u1"), makeMsg("user", "u2")];
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(1);
  });

  test("three API rounds produce correct groups", () => {
    const messages = [
      makeMsg("user", "u1"),
      makeMsg("assistant", "a1"),
      makeMsg("user", "u2"),
      makeMsg("assistant", "a2"),
      makeMsg("user", "u3"),
      makeMsg("assistant", "a3"),
    ];
    const groups = groupMessagesByApiRound(messages);
    // [u1], [a1, u2], [a2, u3], [a3] = 4 groups
    expect(groups).toHaveLength(4);
  });

  test("consecutive user messages stay in same group", () => {
    const messages = [makeMsg("user", "u1"), makeMsg("user", "u2")];
    expect(groupMessagesByApiRound(messages)).toHaveLength(1);
  });

  test("does not produce empty groups", () => {
    const messages = [
      makeMsg("assistant", "a1"),
      makeMsg("assistant", "a2"),
    ];
    const groups = groupMessagesByApiRound(messages);
    for (const group of groups) {
      expect(group.length).toBeGreaterThan(0);
    }
  });

  test("handles single message", () => {
    expect(groupMessagesByApiRound([makeMsg("user", "u1")])).toHaveLength(1);
  });

  test("preserves message order within groups", () => {
    const messages = [makeMsg("assistant", "a1"), makeMsg("user", "u2")];
    const groups = groupMessagesByApiRound(messages);
    expect(groups[0][0].message.id).toBe("a1");
    expect(groups[0][1].message.id).toBe("u2");
  });

  test("handles system messages", () => {
    const messages = [
      makeMsg("system", "s1"),
      makeMsg("assistant", "a1"),
    ];
    // system msg is non-assistant, goes to current. Then assistant a1 is new ID
    // and current has items, so split.
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(2);
  });

  test("tool_result after assistant stays in same round", () => {
    const messages = [
      makeMsg("assistant", "a1"),
      makeMsg("user", "tool_result_1"),
      makeMsg("assistant", "a1"), // same ID = no new boundary
    ];
    const groups = groupMessagesByApiRound(messages);
    expect(groups).toHaveLength(1);
    expect(groups[0]).toHaveLength(3);
  });
});